Temperature, Wind and Frostbite

Frostbite can occur with prolonged exposure to cold temperatures below the freezing point of skin.  When the brain senses a drop in temperature, it signals vessels near the skin to constrict, preserving blood flow to vital organs.  As parts of the body farthest from the heart get colder, blood vessels in extremities will expand and contract periodically to preserve as much function as possible, a condition called the hunter's response.

Once the body's internal temperature drops below 98.6 degrees (F) to the point of hypothermia, these vessels permanently constrict and frostbite has begun.

The wind chill chart above compares frostbite times, with actual air temperature and wind speeds (Credit: NOAA/ National Weather Service).